Conventional high-frequency antennas are often cumbersome to manufacture. For example, antennas designed for 100 GHz bandwidths typically use machined waveguides as feed structures, requiring expensive micro-machining and hand-tuning. Not only are these structures difficult and expensive to manufacture, they are also incompatible with integration to standard semiconductor processes.
Because of the expense and difficulties associated with micro-machined structures, efforts have been made in the research and development of low cost alternatives for antennas, transmission lines, waveguide structures, and planar movable components for sub-THz frequency operation. In particular, aperture-coupled microstrip antennas have been of great interest because such structures inherently offer electromagnetic separation between the radiating patch antenna element and the feed network. However, antenna design using silicon, GaAs and other semiconductor substrates at higher frequencies such as millimeter-wave frequencies suffers from a number of drawbacks. In particular, the high dielectric constant of the semiconductor substrate, for example, ε=11.7 for Si, implies that undesirable surface waves will be readily triggered. Although the power lost to surface waves may be reduced by using relatively thin substrates having a thickness of approximately {fraction (1/10)} the operating wavelength, current semiconductor-based antenna designs generally offer mediocre return losses and efficiency.
Accordingly, there is a need in the art for improved antenna designs that are compatible with standard semiconductor processes and offer low return losses without requiring micromachining.